Simultaneous Microwave Imaging and Parameter Estimation Using Modified Level-Set Method

This paper proposes a hybrid boundary detection method for image based on a new modified level set method and a fuzzy model. It is applied to a boundary detection problem of coronary plaque. Level set method has been applied widely in image processing. It however does not work well for an intravascular ultrasound (IVUS) image because an image gradient, commonly used for calculating a speed function in the level set method, cannot detect an image boundary well. The level set method and the weighted image separability proposed by the authors in the past were applied for a coronary plaque boundary detection problem. The level set method could not however detect the plaque boundary in several regions. One problem was that the candidates of the plaque boundary detected by the weighted separability were unclear in several regions. The other problem was that the IVUS image often becomes shadowed and it contains no texture information there, which is caused by the presence of the guide wire. To overcome this problem, we propose a new modified level set, and we further propose a hybrid boundary detection method based on the new modified level set and the Takagi Sugeno (T-S) fuzzy model for detecting a coronary plaque boundary. The boundary detection accuracy of the proposed method was significantly better than those of the previous methods we proposed in the past.

Vascular segmentation plays an important role in medical image analysis. A novel technique for the automaticextraction of vascular trees from 2D medical images is presented, which combines Hessian-based multiscale filtering and a modified level set method. In the proposed algorithm, the morphological top-hat transformation is firstly adopted to attenuate background. Then Hessian-based multiscale filtering is used to enhance vascular structures by combining Hessian matrix with Gaussian convolution to tune the filtering response to the specific scales. Because Gaussian convolution tends to blur vessel boundaries, which makes scale selection inaccurate, an improved level set method is finally proposed to extract vascular structures by introducing an external constrained term related to the standard deviation of Gaussian function into the traditional level set. Our approach was tested on synthetic images with vascular-like structures and 2D slices extracted from real 3D abdomen magnetic resonance angiography (MRA) images along the coronal plane. The segmentation rates for synthetic images are above 95%. The results for MRA images demonstrate that the proposed method can extract most of the vascular structures successfully and accurately in visualization. Therefore, the proposed method is effective for the vascular tree extraction in medical images.

Fluid drag is a force that opposes relative motion between fluid layers or between solids and surrounding fluids. For a stationary solid in a moving fluid, it is the amount of force necessary to keep the object stationary in the moving fluid. In addition to fluid and flow conditions, pressure drag on a solid object is dependent on the size and shape of the object. The aim of this project is to compute the shape of a stationary 2D object of size 3.5 m2 that minimizes drag for different Reynolds numbers. We solve the problem in the context of shape optimization, making use of shape sensitivity analysis. The state variables are fluid pressure and velocity modeled by the Navier-Stokes equation with cost function given by the fluid drag which depends on the state variables. The geometric constraint is removed by constructing a Lagrangian function. Subsequent application of shape sensitivity analysis on the Lagrangian generates the shape derivative and gradient. Our optimization routine uses a variational form of the sequential quadratic programming (SQP) method with the Hessian replaced by a variational form for the shape gradient. The numerical implementation is done in Python while the open source finite element package, FEniCS, is used to solve all the partial differential equations. Remeshing of the computational domain to improve mesh quality is carried out with the open source 2D mesh generator, Triangle. Final shapes for low Reynolds numbers resemble an american football while shapes for moderate to high Reynolds numbers are more streamlined in the tail end of the object than at the front.

The effective techniques for remediation of sites polluted by dense non-aqueous phase liquids (DNAPLs) remains a challenge. Among the various technical monitoring methods, there is an increasing interest in studying the geophysical characteristics of contaminated soils, as indicators of the progress in clean-up programs. This work sought to investigate the variation of the electrical complex resistivity and the relative permittivity by analyzing the results obtained from spectral induced polarization (SIP) and time domain reflectometry (TDR). Different series of measurements during drainage and imbibition of DNAPLs in porous media were done to validate the clean-up process on sites polluted by DNAPLs. Therefore, a methodology based on laboratory work was designed and carried out to study the electrical complex resistivity (both in magnitude and phase) in the frequency range 0.183 Hz to 20 kHz, and the relative dielectric permittivity at 70 MHz. The experiments were done on small 1D cells. In these cells, glass beads were used as a porous medium. Two different fluid couples, i.e., coal tar (CT)/water and canola oil (CO)/salty ethanol (SE), were used to produce two-phase flow. Our findings highlight that due to the high resistivity of CO and CT, an increase in water saturation led to decrease in amplitude and phase. Saturation change of SE had the same effect on resistivity but no relationship was found for phase and saturation for the mixture CO and SE. It is also showed that the complex resistivity and relative permittivity measurements were compatible with generalized Archie's law and complete complex refractive index method (CRIM) model as two empirical models for defining the correlation between the electrical resistivity, relative permittivity, and saturation of each phase in the multiphase porous medium.

This paper aims to present an effective electromagnetic (EM) modelling approach for rectangular bundle of single-walled carbon nanotubes (RB-SWCNTs), based on the electrical conductivity, relative complex permittivity and linear distribution impedance by applying General Ohm’s law for this bundle. The equivalent single conductor material (ESCM) model for personification the RB-SWCNTs is present in this paper. The main target of this modeling approach is to estimate and investigate the EM properties of RB-SWCNTs using common EM engineering tool solver CST (MWS). For this purpose, the RB-SWCNTs and ESCM dipole antennas will be designed and implemented using CST (MWS). The equivalent conductivity model, relative complex permittivity and other parameters of the RB-SWCNTs will be derived in this paper and considered as an equivalent material parameters for the ESCM. This modeling technique is expected to provide new avenues for designing different antenna structures.

Anterior Regions of Monkey Parietal Cortex Process Visual 3D Shape

The physical parameters of human blood (complex permittivity and conductivity) at microwave frequencies have been investigated to assess the hematocrit (HCT). The cavity perturbation method based on a rectangular cavity operated in TE101 mode at frequency 4.212 GHz has been utilized to measure the permittivity of blood with different hematocrit % at a range of temperatures. According to the results, the dielectric constant, loss factor, and conductivity appeared to be influenced by HCT level. Though the dielectric constant is the only parameter that shows clear linear regression decreasing behavior with a correlation value around (R2 = 0.93). For thirty healthy donors the dielectric constant decreases from (65.61 ± 1.4 to 44.64 ± 4.0) and from (65.3 ± 1.2 to 48.3 ± 1.88) for men and women, respectively, with increasing hematocrit percentage from 20% HCT up to 95% HCT. The temperature dependence of the dielectric constant is also examined in the temperature range 27 °C–50 °C and the results display a slight decrease in dielectric constant with elevation temperature. The temperature-dependence dielectric constant of water and blood samples were fitted to an empirical polynomial with temperature. A comparison of estimated HCT using the cavity technique based on dielectric properties shows a very good agreement with commercially standard HCT measurement methods. Finally, the cavity technique can be applied to measure the hematocrit up to high values based on the dielectric constant with high precision, simplicity, and low cost compared with traditional techniques.

The microwave properties of Glass-coated FeCuNbVSiB and CoFeNiSiB microwires/dielectric composite with different microwires diameters were studied. Relative complex permeability and complex permittivity was measured by transmission/reflection (T/R) coaxial line method at the frequency range of 2-18 GHz for composite samples. The results show that the microwave permeability and permittivity increases with the lengthening of the microwires in composite. The microwave permeability, natural resonance frequency and microwave permittivity increase with the decrease of the diameter of the microwires.

To determine the complex permittivity of material mounted on the metal surface, the free-space reflection method is a good candidate due to its advantages of being nondestructive and contactless. When using the method, the extraction of the complex reflection coefficient (CRC) of the metal-backed material is the key to realize accurate measurement. Traditionally, the free-space reflection method assumes that the interrogating wave is a single plane wave, and the plane-wave reflection model is used. However, a focused beam is usually used in practice for reducing the edge effect that leads to the difference between the actual test scene and the traditional test model. In this study, a focused-wave reflection model is constructed to invert the complex permittivity, where the focused wave is considered as a Gaussian beam. The CRC of the Gaussian beam is deduced by using the plane-wave spectrum technique and plane-wave scattering-matrix (PWSM) theory. Based on the difference between the CRCs of the focused-wave and plane-wave, inverted complex permittivity corresponding to two reflection models is compared. Numerical results are given to show how the errors introduced by the plane-wave assumption are related to the waist size of the incident beam and the thickness and relative complex permittivity of the material. Measurement of a Teflon slab is given to further demonstrate the capability of the proposed procedure.

With the development of electronic components towards miniaturization and integration, permittivity, permeability, loss tangent and other microwave parameters have become the characteristics of new microwave materials. The relative complex permittivity and relative magnetic permeability of solid materials are the most important for microwave electrical elements, componentsor antennas design. In this paper we introduce the method of measuring relative complex permittivity and relative magnetic permeability of solid materials at 30MHz∼50GHz frequencies using air coaxial line and waveguide. The paper describes how to make phase compensation to solve the issue brought by the calibration of the network analyzer and how to re-calculate the S parameters using phase compensation technology.

In this paper, accuracy analysis of Transmission Phase-Shift (TPS) method for material characterization is presented. Dielectric property in materials is one of the characteristics that describe the interaction of material with electromagnetic waves. Understanding the characteristic of some reference materials by measuring its relative permittivity is very important. The value of relative permittivity obtained from TPS method is then compared with the one acquired from Nicholson-Ross-Weir (NRW) method to have more accurate in analysis. To validate the proposed method, some reference materials are performed and compared with the NRW method. The proposed method is verified through the simulation using a WR90 type X-band rectangular waveguide. The characterization results show that the TPS method could cover wider range of relative permittivity than the NRW method. In addition, the method for converting S-parameters to the dielectric property is also demonstrated. The dielectric property, which is extracted from S-parameters and analyzed using the TPS method, can also be in a complex relative permittivity.

This study focuses on the measurement and analysis of the complex permittivities of polymer blends using the field enhancement method (FEM). The blends, consisting of air-powder or solvent-solute mixtures, are placed in a Teflon holder and inserted into the FEM cavity to determine the complex permittivity. The resonant frequency and quality factor of the FEM cavity coupled with the samples provide information on the blends' dielectric constant and loss tangents. To extract the complex permittivities of three specific samples of DC-840, MCL-805, and MCL-Siloxane, we employ effective medium theories and the high-frequency structure simulator (HFSS) together with the measured data. The results reveal that when the volume fraction of the DC-840 solute in the xylene solvent surpasses a specific threshold, the dielectric constants and the loss tangents experience a notable increase. This phenomenon, known as percolation, strongly correlates with the viscosity of polymer blends. The observed percolation effect on the dielectric behavior is further elucidated using the generalized dielectric constant and the Debye model. By employing these models, the percolation effect and its impact on the dielectric properties of the blends can be explained.

Effect of ultrasonics on photographic films: Gangoli, S.G., Almed, R., Pancholy, M., Journal of the Physical Society of Japan, Vol 25, No 5 (November 1968) pp 1500–1506

A simple method for dielectric constant characterization is the full sheet resonance method. In this technique, the dielectric constant is extracted from the resonance frequencies of a parallel-plate waveguide resonator. The standard method cannot be applied to extract the loss tangent. Recently, the full-sheet resonance method has been extended to extract the loss tangent as well. The new method makes use of a new rapid plane solver and resonators with shorted boundaries. The materials properties are extracted by fitting the simulations to measurements. In this paper, we will demonstrate how the fitting process can be automated. In order to extract the dielectric constant and loss tangent, many simulations need to be run to find the parameters that provide the best match with the measurements. This is a computationally expensive approach. We will present a new method based on tracking sensitivity, which provides a parameterized macromodel for the resonators. Using this approach, the simulation data can be expressed as a low-order rational function of the complex permittivity. Hence, varying the complex permittivity to find the best fit can be done in negligible time after the macromodel has been generated. This new method will be applied to extract the dielectric constant and loss tangent of FR-4.

For stereoscopic photography or telepresence, orthostereoscopy occurs when the perceived size, shape, and relative position of objects in the three-dimensional scene being viewed match those of the physical objects in front of the camera. In virtual reality, the simulated scene has no physical counterpart, so orthostereoscopy must be defined in this case as constancy, as the head moves around, of the perceived size, shape, and relative positions of the simulated objects. Achieving this constancy requires that the computational model used to generate the graphics matches the physical geometry of the head-mounted display being used. This geometry includes the optics used to image the displays and the placement of the displays with respect to the eyes. The model may fail to match the geometry because model parameters are difficult to measure accurately, or because the model itself is in error. Two common modeling errors are ignoring the distortion caused by the optics and ignoring the variation in interpupillary distance across different users. A computational model for the geometry of a head-mounted display is presented, and the parameters of this model for the VPL EyePhone are calculated.